Photoreaction of aromatic compounds at α-FeOOH/H2O interface in the presence of H2O2: evidence for organic-goethite surface complex formation

The photoreactions of aromatic compounds were investigated in aqueous dispersions of α-FeOOH(goethite)/H2O2 at neutral pHs. It was found that aromatic compounds could undergo rapid decomposition and mineralization (even to 100% yield) in the presence of both α-FeOOH and H2O2 under UV irradiation, and the degradation rates of the organics were related to their sorption ability of the surface of α-FeOOH and were in the following order: salicylic acid ≈m-hydroxylbenzoic acid>p-hydroxylbenzoic acid≈benzoic acid>p-biphthalic acid>phenol>benzenesulfonic acid. The interactions of salicylic acid and benzenesulfonic acid with goethite were examined by Fourier transform infrared spectroscopy (FTIR), and electron spin resonance (ESR) was applied to detect the intermediate radicals formed in the photoreaction. The effect of pH and foreign ligands on the degradation of salicylic acid, decomposition of H2O2, and formation of dissolved iron was also examined.